Add xlrd to requirements.txt because of scripts/collapse_xsl_to_csv.py
Add xlrd to requirements.txt because of scripts/collapse_xsl_to_csv.py

dmc2015/hall-of-justice,dmc2015/hall-of-justice,sunlightlabs/hall-of-justice,sunlightlabs/hall-of-justice,sunlightlabs/hall-of-justice,dmc2015/hall-of-justice